Typical polymerization processes, and emulsion polymerization processes in particular, result in the formation of a suspension of particles or "latex", often in the presence of a surfactant. Subsequent processing of the latex, particularly washing, depends on first agglomerating the latex particles into particle flocks. The size of the flocks is in proportion to the nature of the polymer, and the degree of coagulation.
Latex coagulation has been performed in the past by subjecting the latex to severe mechanical sheer in specialized multistage coagulator equipment. The object of the imparted sheer is to increase the kinetic energy of the individual latex particles to a level such that, upon interparticle impact, the repulsive force exerted by the particles' surfactant coating is overcome, causing particle agglomeration. Particle agglomeration results in the formation of particle flocks consisting of hundreds or thousands of particles, depending on the nature of the polymer and the degree of coagulation. A satisfactory degree of coagulation in this context may be viewed as the formation of aerated flocks of sufficiently large size, such that the flocks may ascend a wash column with sufficient velocity to avoid column flooding at a given velocity of countercurrent wash water. Particle flocks may be washed in countercurrent wash columns to remove water soluble impurities, such as is disclosed in U.S. Pat. No. 4,128,517, for example.
The degree of coagulation achieved depends primarily on the amount of mechanical shear energy imparted to the polymer, per unit mass of polymer. The degree of coagulation further depends upon the nature of the polymer. For one class of polymers, the polyvinylidene fluoride homopolymers and copolymers, the energy input generally required for coagulation varies from about 0.05 to about 0.5 horsepower-hour per pound of polymer. The specific coagulation energy requirement of a given polymer resin appears to depend primarily on the polarity of the polymer, which interacts with surfactant which may remain in the latex from the emulsion polymerization process.